甑島(鹿児島県)県民の歯列弓の民族科学的研究

Measurements were undertaken on a mixed population of Koshikizima, an isolated islet of Kagoshima Prefecture, which consisted of 456 males and 441 females ranging in age from 2 to 59. Data obtained were analyzed with respect to rate of age growth and sex difference. In additon, a comparison was made of these data among the neighboring inhabitants groups and the population groups of different races in neighboring countries. Results were summarized as follows. Difference with age I. Breadth of dental arch The value for the dental arch breadth in creased with age until 15 to 20 years of age, but it decreased slightly after these period. 2. Length of dental arch The value for the length increased with age until 11 to 15 years of age, but it decreased slightly after that stage. 3. Breadth of lower alveolar bone The maximum value for the breadth of lower alveolar bone was found in subjects in the twenties. 4. Dental arch index There was hardly difference with age in this point. Sex difference Male sudjects exceeded female in the magnitudes of the dental arch breadth of lower alveolar bone and length of dental arch respectively, but there was no appreciable sex difference with respect to the dental arch indices. Difference between the islander groups and neighboring inhabitant groups 1. Dental arch breadth In the dental arch breadth, the islander groups were inferior than the groups of Tanushimaru district with both sexes. The female islander groups were too inferior than the comparable groups of Beppu and Asoo districts in Ohita Prefecture. No appreciable difference was found between the islander groups of both sexes and the comparable groups in Kiuragi in Miyazaki Prefecture. 2. Dental arch length The islander groups of both sexes exceeded those district groups in Kiuragi of Miyazaki Prefecture, in Himeshima of Ohita Prefecture and in Hizi of Ohita Prefecture in the magnitude of dental arch length, but were inferior than the district groups of Asoo of Ohita Prefecture. 3. Breadth of lower alveolar bone The value in the islander groups of both sexes was smaller than that in the comparable group in Shimonoseki city, but when compared with the groups of Yawata city, the femle groups of islanders exceeded the comparable groups of Yawata city in this value. 4. Dental arch index The male groups of the islanders exceeded those groups in Tanushimaru (Fukuoka Prefecture), Himeshima (Ohita Prefecture) and Kiuragi (Miyazaki Prefecture) in this respect. The groups of the islanders showed values larger than those of Yawata female and smaller than those of Shimonoseki female. Difference between racial groups in the neighboring countries 1. Breadth of dental arch The Koshikizima islanders showed larger values than did Formosan but smaller values than did Mongolian and Korean. 2. Length of dental arch The islanders showed larger values than did Mongolian and Manchurian, smaller values than did Formosan and Korean. 3. Dental arch index The value of the indices in the islander groups was larger than those in the Mongorian, Korean and Manchurian race groups but smaller than in the Formosan group.